class Grade {
  Grade({
    this.title,
    this.items,
  })  : assert(title != null),
        assert(items != null);

  String title; //单选  多选 (大题类型)
  List<GradeItem> items; //每小题详情

}

class GradeItem {
  GradeItem({
    this.isRight,
  })  : assert(isRight != null);

  bool isRight; //是否正确
  String id; //小题的id
}
